The brake apparatus installed on railway freight cars being built at the present time includes a brake control valve device that is substantially the same as the brake control valve device shown and described in U.S. Pat. No. 3,175,869, issued Mar. 30, 1965, to Walter B. Kirk and assigned to the assignee of the present application, and a brake cylinder device that is substantially the same as the brake cylinder device shown and described in U.S. Pat. No. 3,183,795, issued May 18, 1965, to Walter B. Kirk and also assigned to the assignee of the present application.
Moreover, as is shown in the above-mentioned U.S. Pat. No. 3,175,869, this railway freight car brake apparatus further includes an auxiliary reservoir and an emergency reservoir which are charged with fluid under pressure from the usual train brake pipe when a brake release is effected, and from which reservoirs fluid under pressure is supplied to the brake cylinder to cause brake shoes to be pressed against the wheels of the freight car when a brake application is effected.
Since these two fluid pressure storage reservoirs are separate items that are necessary in addition to the brake control valve device and the brake cylinder device required for each freight car, it is readily apparent that they increase the total cost of the brake apparatus required on each car.
Accordingly, it is the general purpose of this invention to provide a railway freight car brake apparatus that comprises a novel brake cylinder device that embodies a pair of tandem-connected pistons of unequal diameter, the larger piston cooperating with the brake cylinder body to form on the respective opposite sides of this piston two reservoirs that are charged with fluid under pressure from a train brake pipe. A novel brake control valve device responsive to variations of pressure in the train brake pipe effects the establishment of fluid under pressure forces on the one or the other sides of the two pistons to cause a brake application and a subsequent brake release.